The present invention relates to log debarking machines and more particularly to hollow head log debarkers having a ring rotor through which successive logs are fed. The logs in such debarkers are engaged and stripped of their bark by arcuate debarking tools rotatably supported by the ring rotor. The present invention is further concerned with debarking tool assemblies for such debarking machines.
Generally, the prior art teaches that several debarking tools are mounted around the central opening of the rotor and in their inoperative positions they extend about radially inwards with the debarking tips located close to the axis of the rotor. When the rotor rotates and a log is fed into the rotor inlet or infeed side, the front end of the log strikes the sharp leading edge of the debarking tools and causes them to climb onto the debarking surface of the log against the action of resilient or tensioning means. The leading edges of the tools are thereby caused to climb up on the log surface.
The debarking tools are positioned perpendicular to the flow so that when the log strikes the tools' leading edge the tools have to climb the face of that log to where the tool tip is riding on the debarking surface before the log can travel further. This causes a tremendous shock load to all parts of the debarker. Further, the larger the log diameter the greater the movement of the tool tip to the debarking surface and correspondingly the greater the shock load.
The geometric design of the prior art debarking tools is around the climbing edge so that the larger the log diameter the flatter the tool tip lay back on the log. Since the sharp tool tip is not pointed towards the theoretical centerline of the debarker, the pressure required to debark the logs is great. This causes shock loading, tool breakage, tension pin breakage, tension band breakage, and unnecessary shock to the entire debarker. Further, tools in the past have used a clamp method to retain the debarking tool in or on the tool shaft. This clamping has resulted in excessive shock loading to the tools and loosening of the tool arm in the tool shaft, which causes metal fatigue in the tool mounting area.
The present method of harvesting trees uses a shearing rather than a sawing action to cut the trees down. The shearing causes fractured fiber at the log for logs of all diameters, especially the larger logs. The fractured fiber then does not give sufficient stability for the sharp leading edge of the debarking tool to bite into, with the forces spread out through the entire debarking tool. Thus, the tools cannot efficiently climb the log to mount onto its debarking surface. The operator often will then have to reduce the pressure on the debarking tool, in which case the debarking tool will not remove the bark. Alternatively, the operator can stop each effected log and saw the sheared fiber from the log end, but in addition to slowing the debarking operation fiber is lost. The third alternative is for the operator to stop each effected log and saw it at an angle so that the end of the log can slope behind the debarking tool and mount the log by climbing the angled end of the log to the debarking surface, but, as can be appreciated, this also is an inefficient procedure.